The present invention relates to wireless apparatus, wireless communications systems and methods of operation therefor. In particular, but not exclusively, the present invention relates to radio telephone communications systems.
Radio telephone communications systems are well known. Examples of such radio systems are cellular telephone systems of which the Global System for Mobiles (GSM) is a particular example.
In common with communication systems in general, radio communication systems have limited available bandwidth. Indeed, the problem of limited bandwidth availability is typically more acute in radio communications systems than in other types of communication systems. Consequently, the bandwidth available for each communication channel set up by the communications system is limited. Generally, there is a trade-off between a high quality communication, such as one utilising a high data rate encoded speech signal, and the available bandwidth. Another limitation is that radio communication systems typically utilise channel coding, such as error detection/correction coding, which is necessary due to the corruption of communications during transmission. Thus, further limitations are placed on the data rate available transmissions such as for speech coding.
In radio telephone systems, it is known to operate at different speech coding rates and it has been proposed to switch between different coding rates in dependence upon the quality of the radio communication channel; (see European Telecommunications Standard Institute draft specification EN301XXXV2.0.0 (1999-02) xe2x80x9cdigital cellular telecommunication system (phase 2+); adaptive multi-rate speech processing functions; general descriptionxe2x80x9d (GSM) 06.71 v 2.0.0 release 1998) incorporated herein by reference. This document proposes the use of higher data rate speech encoding for communication channels having high quality, that is to say a low level of corruption and hence reduced level (number of bits) of channel coding, and vice versa.
The proposed operation of the system disclosed in the draft specification referred to above requires the channel quality for communications between a cellular radio telephone base station and a mobile station to be measured by a channel quality estimation unit by way of monitoring the signal received at the respective base station and mobile station. Based on the measured signal quality, the base station can send an instruction to a mobile station to switch the coding rate for transmissions therefrom, and also an indication of the coding rate which the base station is using for the downlink (base stationxe2x80x94mobile station) channel. Additionally, the mobile station may request the base station to switch rates by sending an appropriate command request and also inform the base station as to what coding rate the mobile station is using for transmission on the uplink (mobile stationxe2x80x94base station channel). Thus, before each coding rate switch, the appropriate signal quality has to be measured and suitable requests and commands exchanged between the mobile station and the base station.
In the applicant""s co-pending European Patent Applications Nos 99 401571.7 and 99 401573.3, radio apparatus, communications systems and methods for operation thereof are disclosed in which a steerable beam antenna for a radio apparatus is utilised to steer an antenna beam in a direction corresponding to an optimum signal or communications quality. The apparatus searches for the optimum signal quality direction in accordance with a disclosed search strategy. The particular details of operation of the steerable beam antenna need not be disclosed for an understanding of the instant invention and shall not be described further. It is merely sufficient to understand that an optimum antenna beam direction can be identified and the antenna beam directed in that direction.
Another example of the use of a directional beam antenna is disclosed in U.S. Pat. No. 5,303,240, issued Apr. 12, 1994.
Embodiments of the present invention seek to address one or more of the drawbacks or limitations of known wireless apparatus and systems and to preferably improve the performance thereof.
Particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Combinations of features from the dependent claims may be combined with features of the independent claims as appropriate and not as explicitly set out in the claims.
In the following, the term directional beam antenna refers to an antenna for which the radiation pattern for transmission and reception may be varied from an omni-directional radiation pattern to a radiation pattern having a particular beamwidth and direction. The width and direction of the beam may be independently varied.
In accordance with a first aspect of the present invention, there is provided a first wireless communications apparatus for a wireless communications system comprising:
a directional beam antenna;
an antenna controller for directing said directional beam antenna in an optimum signal quality beam direction; and
coding means operable at two or more coding rates, and further operable to switch between said rates responsive to said controller initiating a change in said antenna beam direction.
In accordance with a second aspect of the present invention there is provided a method for operating a first wireless communications apparatus having a directional beam antenna in a wireless communications network, the method comprising:
directing said directional beam antenna in an optimum signal quality beam direction; and
switching between two or more coding rates for communications by said wireless apparatus responsive to initiation of a change in said antenna beam direction.
In accordance with a third aspect of the invention, there is provided apparatus for a wireless communications network, the apparatus comprising:
means for determining a period of inactivity for said apparatus;
means for determining signal quality of a signal received during said period of activity; and
coding means operable at two or more coding rates and responsive to a determined signal quality to switch between coding rates.
In accordance with a fourth aspect of the invention, there is provided a method or operating wireless apparatus, comprising:
determining a period of inactivity for said radio apparatus;
determining signal quality of a signal received during said period of inactivity; and
switching between two or more coding rates for communications by said wireless apparatus responsive to a determined signal quality.
Embodiments in accordance with various aspects of the invention initiate rate switching in accordance with signal quality without the need for further processing of the received signals, such as signal quality measurement and may even obviate the need for the exchange of command/request communications between the first wireless apparatus and a wireless communication systems to switch coding rates. Furthermore, monitoring and measurement of signal quality may be conducted in periods of inactivity. Thus, changing the coding rate may be achieved more quickly with less processing than required with the previously proposed systems. Furthermore, such an embodiment benefits from a synergy between the optimisation of beam direction providing improved signal quality and the initiation of coding rate switching.
In a preferred embodiment, the third aspect of the invention includes a directional beam antenna; and
an antenna controller for directing said directional beam antenna in an optimum signal quality direction in accordance with said determined signal quality, said coding means responsive to said antenna controller initiating a change in said antenna beam direction to switch between said coding rates. Thus, antenna beam switching may be conducted during inactive periods, thereby not imposing a further processing overhead during transmission or reception of speech or data, i.e. traffic signals.
Preferably, the signal is received whilst the period of inactivity comprises a broadcast signal. In an embodiment of the invention operable for a cellular radio communications system, the broadcast signal comprises a signal from a base station with which said apparatus is in primary communication. Optionally, the broadcast signal comprises a signal from any one of one or more base stations for cells adjacent the cell defined by said base station with which said radio apparatus is in primary communication.
Suitably, the period of inactivity comprises a period determined as being designated for the transmission and/or reception of redundant information. In aaparatus operable for speech communication, the period of inactivity comprises non-active segments during transmission and/or reception of silence identity (SID) information. In particular, the non-active segments comprise an empty frame and/or part thereof during transmission of SID frames.
Optionally, for apparatus operable to transmit data, the period of inactivity comprises a period subsequent to an end of data signal transmitted and/or received by said radio apparatus.
In a preferred embodiment, the coding means is a speech coder, sometimes referred to as a speech codec. For such a preferred embodiment, the coding means is operable to switch to higher rate speech coding responsive to said antenna controller directing said directional beam antenna to said optimum signal quality beam direction. For a communication system in which the available bandwidth for any communication is fixed, an increase in the coding rate for the signal e.g. speech signal, would result in a corresponding decrease in the bit rate for channel coding. A reduction in the channel coding bit rate is consistent with there being an improvement in the signal or communication quality, since there would be less need for error correction/detection. Thus, the synergy between the optimisation of beam direction providing improved signal quality and limitation of higher speech coding is clearly expedited.
Typically, the first apparatus is operable to communicate a request to a second wireless communications apparatus in communication with the first apparatus to utilise said higher rate coding responsive to said antenna controller directing said antenna beam to said optimum signal quality beam direction. Correspondingly, the coding means is operable to switch to higher rate coding responsive to a rate switch request communicated from second apparatus in communication with the first apparatus initiated by a change in antenna beam direction for a steerable beam of said second apparatus.
Thus, second apparatus in communication with the first apparatus can be instructed or can instruct a coding rate switch based on antenna beam switching and without further measurement of the signal communication quality.
Typically, the first apparatus is operable to utilise a coding rate corresponding to a coding rate utilised by the second apparatus in communication with the first apparatus, such that both parties to a communication utilise the same coding rates.
In a particularly advantageous embodiment, the first apparatus further comprises an orientation sensitive sensing means, the coding means being responsive to a signal from the sensing means indicative of a change of orientation of the first apparatus to inhibit the coding means switching rates. Additionally, or optionally, the first apparatus may be responsive to change of orientation to inhibit requesting a coding rate switch. Such an advantageous embodiment reduces the likelihood of the coding rate being increased at around the time that a decrease in signal communication quality, and thus a corresponding need for the coding rate to be reduced in order to compensate for the reduction in signal or communication quality, occurs such as when the first apparatus is moved in a manner to move the antenna beam direction away from the optimum beam direction.
In particular, the coding means may be responsive to a signal from the sensor indicative of a sudden change of orientation of the first apparatus. Such an embodiment would inhibit coding rate switching only when there was a high likelihood of a deterioration in signal or communication quality due to rapid changes in orientation of the first apparatus. Additionally, inhibiting coding rate switching due to sensing changes in orientation of the first apparatus reduces undesirable oscillation between coding rates.
In a fifth aspect of the present invention there is provided a first wireless communications apparatus for a wireless communications network, comprising:
coding means operable at two or more coding rates and responsive to control signals to switch between said two or more coding rates; and
a motion sensing means;
said coding means responsive to a signal from said sensing means indicative of a change of orientation of said first apparatus to inhibit switching of said coding means between said two or more rates.
In a sixth aspect of the present invention there is provided a first wireless communications apparatus for a wireless communications network, comprising:
coding means operable at two or more coding rates and responsive to control signals to request a transmitter in communication with said first apparatus to switch between one of two or more coding rates; and
an orientation sensitive sensor;
said coding means responsive to a signal from said sensing means indicative of a change of orientation of said first apparatus to inhibit said request to said transmitter.
In a seventh aspect of the present invention there is provided a first wireless communications apparatus for a wireless communications network, comprising:
coding means operable at two or more coding rates and responsive to control signals to switch between said two or more coding rates; and
motion sensing means;
said coding means responsive to a signal from said motion sensing means indicative of said first apparatus being stationary to switch or request switching between non-adjacent coding rates.
In a particular embodiment of the present invention, there is provided a radio communications station comprising a user interface including a display, a keypad or keyboard for inputting data or commands to the communications station, a transceiver and an antenna operably coupled to the transceiver, and further comprising apparatus as described in the foregoing paragraphs. Preferably, the communications station is a mobile station.
Embodiments of the invention may comprise computer programs, or computer readable media embodying computer programs.
The term xe2x80x9ccodingxe2x80x9d is used throughout the specification and claims to include coding and decoding as the context permits.
Although the present invention finds particular application to cellular radio systems and mobile stations therefor, it also finds application to other wireless communication systems and apparatus, for example Public Mobile Radio (PMR), and the terms wireless or radio communication system and wireless or radio telephone systems include such other systems.